The leader of Reform UK in Scotland, Malcolm Offord, has been dismissed as “tone deaf” and “entitled” after he boasted in a televised election debate about the number of cars, houses and boats he owned.

Responding to the row on Wednesday morning, the SNP leader, John Swinney, proposed that all party leaders should publish their tax returns before the election on 7 May.

Offord, a multimillionaire financier and former Conservative life peer who defected to Reform and was announced as the party’s first Scottish leader in January, told the STV debate on Tuesday evening: “I went to London 40 years ago with £2,000 of debt.

“Full of ambition, I worked hard and I was successful. Today, I own six houses, five cars and six boats. In a 40-year business career I’ve employed hundreds of thousands of people and paid £45m in tax.”

Offord made the remarks during a section of the programme where the six party leaders questioned one another. He asked the co-leader of the Scottish Greens, Ross Greer: “In your Scotland, do you want more people like me, or fewer people like me?”

Greer replied: “Fewer people like you,” adding: “I’m glad you’ve finally admitted how many homes you have, Lord Offord.”

Offord, a yachting enthusiast who also collects classic cars and recently bought a mansion on the banks of Loch Lomond for £1.6m without a mortgage, has previously refused to say how wealthy he is, claiming that is a private matter.

Greer continued: “I think at this point in the debate, it’s worth pointing out there are three times as many holiday homes and empty properties in this country as there are homeless children.”

He told Offord: “You don’t need six homes, you don’t even need two homes, everyone just needs a home to live in.

“Surely if we’re to tackle the housing emergency, the super super-rich elite individuals like you should be giving up some of those homes so people who desperately need a roof over their head actually have somewhere to live.”

Later in the debate, the final televised clash of the campaign ahead of the election, the Labour leader, Anas Sarwar, called Offord “entitled”.

Sarwar said: “The idea that he will stand up for working people is for the birds.”

Speaking to media at a campaign event in Edinburgh, Swinney said: “I thought it was a revelation that was tone deaf. Lord Offord was essentially bragging about his wealth and I don’t think that is the way to engage with voters.”

Swinney indicated he would be “very happy” to publish his own tax return, and see other party leaders do so before 7 May.

Offord drew criticism from opponents earlier in the campaign for missing a weekend’s campaigning to sail his yacht Braveheart in a regatta race in the Channel. At the time, Offord laughed off the criticism, saying: “I’m trying to take this seriously, I mean heaven forbid a man has a hobby, right?”

Anti-poverty and housing campaigners in Scotland privately expressed frustration that they were not able to respond directly to the remarks because of strict pre-election rules.

On a recent BBC Scotcast podcast, Chris Birt, the Scotland director of the Joseph Rowntree Foundation, spoke about the importance of sharing wealth in Scotland, saying: “It’s not a sustainable position where people can have multiple homes where there are people in our country who have none.”